The present invention relates to the interchangeability of plumbing supplies, and more particularly to a method and means for adapting the stem of a plumbing valve unit so that a desired type of plumbing trim can be used therewith, even through the desired plumbing trim is initially incompatible with the stem.
For purposes of the invention described herein, the term "plumbing trim" will be used to described those components of a plumbing fixture that are readily visible and accessible to a user. Of particular import to the present invention, the term "plumbing trim" includes a handle that engages a stem or shaft of a plumbing valve. By manually turning the handle, the valve can be fully opened, closed, or set to any position inbetween, thereby allowing hot and/or cold water to be selectively delivered to a nearby spout. In order for the handle to securely grip the valve to which it is attached, so that any rotation of the handle is transferred to an equivalent rotation of the valve stem, it is common in the art to have a spline or key-pattern at the end of the valve shaft. A mating or matching keyway is then included as an integral part of the handle. The spline of the stem then fits snugly into the keyway of the handle or trim, typically secured by an axial screw, and the fitted spline/keyway thus provides for the efficient transfer of torque from the handle to the stem. That is, the spline of the stem acts as a key that becomes lockingly engaged with the keyway of the handle so that the handle cannot turn without also turning the valve stem. The axial screw does not contribute to the transfer of torque from the trim to the stem, rather it merely ensures that the spline and keyway remain lockingly engaged and do not axially separate.
It is common in the art for plumbing valve manufacturers to provide both the plumbing valve--that unit which is mounted behind the wall or under the counter--as well as the plumbing trim that is used therewith. Most manufacturers, in fact, incorporate a unique spline/keyway design for their valve stem/trim combinations so that only their trim can be used with their valves. In other words, in general, there is no valve/trim compatibility in the plumbing industry. Thus, in general, Price Pfister trim can be only be used with Price Pfister valves; American Standard trim can only be used with American Standard valves; Borg Warner trim can only be used with Borg Warner valves, and so on. (There are many more valve/trim manufacturers than the three named.)
The incompatibility problem is especially acute in two situations. In the first incompatibility situation, a decision is made (for whatever reason) to change the existing trim. For example, it may be necessary to replace the existing trim because it has broken. It may also be desirable to upgrade the existing trim to a different style during construction or remodeling, or to change the trim so that it matches the trim in another part of the house. Whatever the reason, it often happens that the particular new trim that is wanted is only available from one manufacturer, and that is not the manufacturer of the valve unit that is already in place. Hence, a decision must be made as to whether to chose another kind of trim, available from the same manufacturer who manufactured the existing valve unit, or whether to buy a complete new valve unit, including trim, to replace the old valve unit. Replacing the old valve unit, unfortunately, is usually not a trivial task. It often involves tearing into the wall where the old valve unit is located (especially when the valve unit is used with a tub or shower) and usually ends up being a very messy, time consuming, and expensive job, even for the most experienced plumbers or handymen. Unfortunately, replacing the old valve unit may be the only option available in those situations where the valve unit was installed many years earlier and the valve manufacturer is no longer in business, or there is no acceptable compatible trim available in the market place.
In order to solve the problem created by this first situation (of wanting to change the trim), it is known in the art to provide universal trim that allegedly "fits all" stems. Unfortunately, the mechanism used to accomplish this universal fitting arrangement involves the use of set screws that engage the existing spline at various points around the circumference of the spline. Alternatively, a single set screw is used to engage the spline and stationary teeth on the opposite side of the spline from the set screw are pressed into engagement with the spline as the set screw is tightened. In either embodiment, because only a limited number of contacts are made with the spline by the set screws or stationary teeth, and because the stem and splines are typically made of brass (a relatively soft metal that is used for it anticorrosive properties), it is usually only a matter of time, after successive tightenings, before the set scres or stationary teeth have sufficiently chewed up the spline so that the second incompatibility problem, as described below, exists (broken or unusable spline). Further, the need to use set screws that radially engage the spline or stem as they are tightened requires that access to these screws be provided. This usually requires that unsightly access holes be included in the trim.
In the second incompatibility situation, the valve stem breaks, thereby providing no spline to which any trim can be attached. In this second situation, the only alternative known in the art is to replace at least the valve stem. Unfortunately, as seems to happen more often than not, the valve unit is an older unit whose manufacturer has since gone out of business, or who no longer makes replacement parts for the particular valve unit needing its stem replaced, meaning that no replacement valve stem is available. Hence, the entire valve unit must be replaced, which can be a very messy and expensive job, as indicated above.